When cladding a precious metal to a precipitation hardenable base metal, thermally induced diffusion (or interdiffusion) between the metals is common. The result is diminished purity of the precious metal. Because interdiffusion is a function of temperature, it becomes significant when cladding with base metals of relatively high annealing temperatures, e.g., beryllium-copper alloys.
To compensate for interdiffusion, substantial amounts of precious metal have been used in excess of that required for the finished product, i.e., electronic connectors. For this reason, beryllium-copper alloys have been found relatively costly for use as a base metal.
Conventional copper alloys with relatively low annealing temperatures such as phosphor bronze are processed, e.g., by cladding, with minimal interdiffusion. While relatively economical for use as a base metal, phosphor bronze lacks the strength, ductility and conductivity of beryllium-copper alloys.